modules/common-http/src/main/java/org/apache/tuscany/sca/common/http/HTTPUtils.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.tuscany.sca.common.http;

import java.math.BigInteger;
import java.security.MessageDigest;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 *  @tuscany.spi.extension.asclient
 *
 */
public class HTTPUtils {

    /**
     * Utility method to set common http headers and other stuff in a
     * default http response. Applications / Extensions can then override and
     * tweak as they see fit.
     *
     * @param response
     */
    public static void prepareHTTPResponse(HttpServletResponse response) {
        response.setDateHeader("Date", System.currentTimeMillis());
    }

    /**
     * Calculate the relative request path taking in consideration if
     * the application is running in a embedded webContatiner or from
     * within a web application server host environment
     *
     * @param request The http request
     * @return the relative path
     */
    public static String getRequestPath(HttpServletRequest request) {
        // Get the request path
        String contextPath = request.getContextPath();
        String servletPath = request.getServletPath();
        String requestURI = request.getRequestURI();

        int contextPathLength = contextPath.length();
        int servletPathLenght = servletPath.contains(contextPath) ? servletPath.length() - contextPath.length() : servletPath.length();

        String requestPath = requestURI.substring(contextPathLength + servletPathLenght);

        return requestPath;
    }

    /**
     * Calculate the context root for an application taking in consideration if
     * the application is running in a embedded webContatiner or from
     * within a web application server host environment.
     *
     * In the case of webContainer the contextRoot will always be a empty string.
     *
     * @param request The http request
     * @return the contextRoot
     */
    public static String getContextRoot(HttpServletRequest request) {
        // Get the request path
        String contextPath = request.getContextPath();
        String requestURI = request.getRequestURI();

        int contextPathLength = contextPath.length();

        String contextRoot = requestURI.substring(0, contextPathLength);

        return contextRoot;
    }

    /**
     * Calculate the ETag using MD5 Hash Algorithm
     * @param content the content to hash
     * @return
     */
    public static String calculateHashETag(byte[] content) {
        String eTag = "invalid";
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            byte[] digest = messageDigest.digest(content);
            BigInteger number = new BigInteger(1, digest);
            StringBuffer sb = new StringBuffer('0');
            sb.append(number.toString(16));
            eTag = sb.toString();
        } catch(Exception e) {
            //ignore, we will return random etag
            eTag =  Integer.toString((new java.util.Random()).nextInt(Integer.MAX_VALUE));
        }
        return eTag;
    }
}